Large negative tension-impedance effect in a soft ferromagnetic microwire

Abstract

Large negative tension-impedance effect was found in a soft ferromagnetic FeCoNiBSiMo microwire, namely, the impedance of the microwire was greatly reduced by the presence of mechanical tensions at intermediate frequency. The impedance reductions could be attributed to the sharp declines of the cylindrical permeability induced by the mechanical tensions. High-frequency skin effect was decreased after stretching the microwire in the longitudinal direction, and the surface current of which redistributed due to the presence of mechanical tensions. A strong tension-resistance effect was found at high frequency, while a strong tension-inductance effect was found at low frequency. Significantly, the decreased skin effect in a stretched microwire is especially suitable for the development of high-frequency tension-impedance sensors requiring small impedance.

Advantages of Bistable Microwires in Digital Signal Processing

“…The time intervals measurement presents a fundamental advantage of employing bistable microwires into the measurement chain because the size of the microwire response amplitude is irrelevant, but the time at which the switching field is reached matters. The time at which the switching field is reached is called the switching time (t1 and t2 in Figure 4) [24][25][26][27][28][29][30][31]. In the scenario where the excitation coil magnetizes the bistable microwire without any additional external magnetic field, t 1 = t 2 .…”

“…Such dependencies can be used for sensing applications [ 24 , 25 , 26 , 27 , 28 ]. Contrary to the classical magnetic sensors based on permeability variation, bistable wires are characterized by low permeability (comparable to the permeability of a vacuum) [ 29 , 30 , 31 , 32 ]. On the other hand, the contribution of the magnetic field, temperature, or stress to the switching field can be easily separated using the triangular shape of the excitation field and properly selected chemical composition.…”

“…Generatin odic signal that can be adjusted by properly selecting the frequency of the excitati it is possible to filter the signal even in the case of extremely noisy environments Separated paragraphs should be dedicated to the positive magnetostrictive microwires. Due to the (mainly axial) stresses introduced during production, their domain structure consists of a single axially magnetized domain, which is magnetized in the single large Barkhaussen jump of the closure domains that appears naturally to decrease the stray fields [24][25][26][27][28][29][30][31]. As a result, such wires show magnetic bistability, i.e., their magnetization state is characterized by only two states-positive or negative saturation (see Figure 2).…”